The potential for adaptation

One of the great discoveries within population genetics in recent times is that most phenotypic traits appear to have higher capacity to evolve than previously assumed. However, different types of organisms and traits differ tremendously in their evolvability, and many traits appear inexplicably conservative or maladaptive. There is a need to develop theoretical models and empirical model systems to better understand and predict why some traits evolve readily and others do not.

Although evolvability is initially determined by the amount of genetic variation that selection can act upon, it is becoming increasingly clear that only parts of this variation may be useful for adaptation. Formal analytical models have been developed to describe how genetic architecture (patterns of pleiotropy and epistasis) affects evolutionary capacity by structuring character variability. This has lead to new hypotheses about the links between genetic architecture and evolvability, and identified novel genetic parameters in need of empirical estimation. Further work with theoretical models will investigate these hypotheses and parameters in explicit gene-regulatory networks, and develop methods for their estimation.

Parameters describing epistatic and pleiotropic constraints can be based both on classical quantitative-genetic breeding designs and on Quantitative Trait Loci (QTL) analysis. We will attempt to estimate these parameters using different empirical systems. For instance, various types of quantitative-genetic analysis will be undertaken on the grayling system to understand genetic potential, and the genetic basis of phenotypic differences among recently diverged populations. Information about possible genetic constraints will be checked against the actual patterns of diversification.

Learning and plasticity have been seen both as drivers of and constraints on evolution. Either by inducing novel selection pressures by allowing organisms to explore new ways of living (the Baldwin effect), or as buffers against evolutionary change by stabilizing the niche. Most studies of learning have focused on animals in captivity. With our model systems of passerine birds, we can undertake pioneering experiments on life-time reproductive success of cross-fostered and control birds in the wild. We will study evolutionary consequences of sexual selection by female choice and species recognition in hybrid zones depending on whether traits are culturally (e.g., song) or genetically inherited (e.g., plumage colour). Using the same experimental passerine bird system we will assess to what extent climate change has lead to evolutionary changes in migration timing. This will be done by estimating fitness components based on the accumulated data from our longterm studies on the pied flycatcher.

Selective harvesting is potentially a strong evolutionary force. For both fish and mammals we will assess how harvesting affects multiple traits (such as age and size at maturation, reproductive investment and immature growth) and then compare these results with estimates of the evolvability of such traits. For instance in pike and Atlantic cod harvesting selects for reduced growth and thus smaller body size and decreased reproductive potential. This phenomenon has consequences for management and may also apply to mammals such as deer. Another important aspect of harvesting that we will study is the relative roles of active selection (induced by human practice) and passive selection (due to animal behaviour, harvesting method, etc.).